How Does It Work: Hydropower

Hydropower – power generated using water’s downhill flow – is one of the most common alternatives to fossil fuels. But while hydropower boasts significant advantages over energy sources like oil and coal, it also creates some serious problems of its own.

What is hydropower?

Water has been used for power in almost every society since ancient times. The Egyptians harnessed the Nile for irrigation, and Romans used water-powered mills to grind grain. Today, we use a variety of methods to turn the power of water into electricity, with about 16% of global energy coming from hydroelectric sources.

Hydroelectric dams: Dams are what most of us think of when we hear about hydroelectric power. These giant walls of concrete back up rivers to form large, artificial lakes and then move the water through narrow channels to drive electric generators. The largest hydropower plants in the world are all conventional dams, including the Three Gorges Dam in China and the Grand Coulee Dam in Washington (the largest hydroelectric plant in the U.S.). The world’s largest dam – the Itaipu, which straddles Brazil and Paraguay – generated over 90,000 GWh in 2001: that’s enough to power over 10 million homes!

While hydroelectric dams are valued because they don’t rely on fossil fuels (and therefore produce no greenhouse gas emissions), they come with their own set of serious environmental problems. These dams work by stopping a river to create a reservoir, which is incredibly damaging to natural ecosystems. In addition to preventing the movement of wildlife up and down the river, dams remove the natural water supply to areas downstream while covering upstream areas with a brand-new lake. In short, the entire ecosystem surrounding the dam is reorganized, wreaking havoc on local plant and animal life. The Three Gorges Dam, for example, is situated in one of China’s most biodiverse areas and has negatively affected hundreds of species, from endangered river dolphins to migrating Siberian Cranes. It’s also common for large numbers of people to be moved to accommodate conventional hydroelectric dams.

Pumped storage: Water can also be used to store energy. Pumped storage facilities use low-cost, off-demand electricity to move water up to reservoirs, which can then be used to make electricity during peak demand periods. Pumped storage facilities are similar in design to conventional dams and create many of the same environmental problems.

Run-of-the-river: Run of the river power plants create energy in much the same way as conventional dams, but they don’t require the creation of a large, artificial reservoir. Instead, these facilities use the natural flow of a river to move water, which makes them much less damaging to the environment. However, it also means they can be disrupted by natural changes in a river’s activity due to seasonal droughts or heavy rainfall, so they are not as common as conventional dams.

Tidal and wave power: Because conventional hydroelectric dams can cause so many environmental problems, people have been looking for new ways to harness the power of water. One of these is tidal power, which uses the natural flow of water during tidal movement to generate electricity. Small tidal power stations have been in use since the 1960s, but the high cost and difficulty of finding suitable locations has slowed the development of the technology. Wave power operates in a similar fashion by using the force of waves to operate a turbine to create electricity. The technology is only in its experimental phase at the moment, but many hope it can prove a valuable alternative to not only fossil fuels but also conventional, and more damaging, hydroelectric dams.

How does hydroelectric power affect you?

Chances are that hydroelectric power plants don’t directly affect your home. It’s currently the most-used renewable power source, but still only about 7% of energy produced in the U.S. comes from hydropower. But no matter how you power your home, the environmental impact of hydroelectric dams is an issue that affects us all, and to live green it’s important to appreciate not only hydroelectricity’s role as an alternative to toxic fossil fuels but its problems as well.